Clean-burning aviation gasoline additive to eliminate valve seat recession and deposits

ABSTRACT

A fuel additive for fuel formulations comprising calcium sulfonates in an amount effective to limit or eliminate valve seat recession in engines utilizing such fuel formulations. The fuel additive may also include a detergent, particularly in an amount to enhance the VSR limiting effect of the calcium sulfonates. Also included are fuel formulations containing calcium sulfonates in a concentration effective to limit vale seat recession in engines utilizing the fuel formulations. Methods for treating VSR in piston engines are also provided.

FIELD OF INVENTION

Valve Seat Recession (VSR) can occur in any internal combustion enginedue to the repetitive impact of the valves in the cylinder, particularlythe exhaust valve, contacting the cylinder head socket (valve seat)under intense temperature and pressure over the operating life of apiston engine.

BACKGROUND

Combustion of gasoline products in the combustion chamber of a pistonengine often results in residue and deposits forming around the intakevalve and exhaust port and around the cylinder and piston head. Thecomposition of gasoline typically comprises C₇-C₁₀ aromatic hydrocarbonsand C₄-C₁₂ aliphatic compounds that upon incomplete combustion result inengine deposits and combustion residue.

The cleanest combustion examples, i.e. those unleaded gasolines thatcontain only C₄-C₁₀ aliphatic compounds and high-octane oxygenatedcompounds (e.g. ETBE, MTBE, TAME, alcohols, etc.), tend to offer muchcleaner combustion characteristics due to the presence of oxygen intheir chemistry. However, many high performance gasolines with moreexotic high-octane chemistries often do not fully combust. This canresult in the combustion chamber being effectively “too clean” withoutthe help of an effective valve seat recession additive.

Alternatively, these fuels may utilize specific compounds known asoctane boosters, e.g. aromatic amines, organometallic compounds, or >5%(m/m) aromatic hydrocarbons. Typical high-octane compounds used to boostoctane rating in gasoline engines, but that often result in heavierengine, sparkplug and valve-seat deposits, may include any of thefollowing: aromatic hydrocarbons (e.g., toluene, xylenes, andtri-methylbenzenes); aromatic amines (e.g., aniline, m-toluidine andCumidine); and organometallic compounds (e.g. tetraethyllead (TEL), MMT(Methylcyclopentadienyl manganese tricarbonyl and ferrocene).

The octane boosters increase octane ratings of the fuel but tend tocause dirty build-up of deposits and grime in the combustion chamber.This can create a physical barrier, primarily around the exhaust port,which serves to resist valve seat recession. However, this type ofbuild-up can become excessive, leading to loss of compression in thecombustion chamber or even engine shut-down - thus such excessivedeposits require frequent servicing and diligent cleaning of the sparkplugs, often every 25 to 50 hours of engine operation in certain engineapplications.

There is a long history of using VSR additives in gasoline to prevent orminimize valve seat recession. However, such additives have focused fordecades on the use of phosphorous-based compounds, potassium, sodium andmanganese organometallic chemistries (see Technical Committee onPetroleum Additive Manufacturers in Europe—(ATC) document 113 publishedin September 2013).

Traditional phosphorous, potassium, sodium and manganese anti-VSRadditives blended with gasoline or aviation gasoline in an aircraftengine tend to develop specific unwanted effects, such as increased wearat other parts of the engine and layers of sludge on the combustionchamber making an uncontrollable amount of deposits that may require achemical scavenger to abate. Chemical scavengers often add to toxicityconcerns and add complexity to the combustion and exhaust behavior ofthe fuel.

Fuel additives determine much about the useful nature of any gasoline.TEL is toxic and although it is present in small amounts (˜2.1 gPb/gallon), it has a large impact on airborne and municipal watertoxicity levels across the nation. Aviation gasoline is one type ofpremium-quality gasoline for somewhat lower-compression piston enginesthat has historically contained TEL, which tends to create what issometimes referred to as a lubricity effect which serves to preventvalve seat recession.

Such leaded gasoline is also coupled (2:1) with ethylene dibromide, aneven more toxic compound as a chemical scavenger of the lead. Togetherthese compounds directly affect the level of sludge in an engine, thefrequency of oil changes, the frequency of sparkplug changes due to leadfouling, the consternation of communities dealing with exhaust toxicityof micro-particulates of lead dust. The seemingly small quantity ofadditives determines a lot about the nature of the fuel. See Table 1.

TABLE 1 Old Fuel Additives Impact of Key Fuel Additives Anti-VSRDetergents Unintended Side Effects Auto Gasoline NR; 5-50% aromaticsAlready in use Toxic exhaust without catalytic convertor 100LL Avgas NR;Lead deposits Lead too thick Frequent service to remove lead; Toxicexhaust 100R Avgas Test Min 10 ppm calcium Up to 250 ppm None - Resultsin longer service intervals 100-MMT Avgas NR; MMT deposits MMT too thickFrequent service to remove MMT; Toxic exhaust 100-Amine Avgas NR; >5%aromatics May be useful Monitor fuel system for amine damage NR = NotRequired due to the chemistry of the fuel causing excessive combustionchamber deposits

SUMMARY OF INVENTION

A fuel additive is provided to limit valve seat recession in pistonengines. The additive provides calcium sulfonates in an amount in fuelformulation effective to limit VSR in engines using the fuelformulation. The calcium sulfonates preferably comprise calciumpetroleum sulfonates, and the fuel additive may also include detergents,antioxidants and anti-microbial agents. The additives find particularuse with clean-burning aircraft fuels. Also provided are methods fortreating vale seat recession in engines by combining the fuel additivesto the fuel used by such engines. Further provided are fuel formulationscontaining calcium sulfonates, and optionally detergents and othercomponents, which result in limited valve seat recession in the enginesusing such fuels.

Key features of the Additive package in this invention are its abilityto limit, or even prevent, valve seat recession (VSR), eliminate intakedeposits, and protect against corrosion and microbial growth in theaircraft.

This invention utilizes a new technology—a specialized gasolineadditive—to limit valve seat recession (VSR), including when using aclean-burning gasoline, preferably an unleaded gasoline.

Furthermore, such gasolines, particularly clean-burning gasolines, usingthis invention result in far less corrosion in the engine and oil system(typically caused by the presence of organometallics) leading to longerengine life and longer time between engine overhauls.

A preferred embodiment is a high-octane premium-quality aviationgasoline comprised of aliphatic hydrocarbons and oxygenates with no orvery low levels of aromatics, amines or metals as outlined herein.

Further forms, objects, features, aspects, benefits, advantages, andembodiments of the present invention will become apparent from adetailed description and drawings provided herewith.

DESCRIPTION

For the purpose of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments and specificlanguage will be used to describe the same. It will nevertheless beunderstood that no limitation of the scope of the invention is therebyintended. Any alterations and further modifications in the describedembodiments, and any further applications of the principles of theinvention as described herein are contemplated as would normally occurto one skilled in the art to which the invention relates. One embodimentof the invention is shown in great detail, although it will be apparentto those skilled in the relevant art that some features that are notrelevant to the present invention may not be shown for the sake ofclarity.

This invention uses a special formulation of components blended insolution as a fuel Additive (the “Additive”) which is added at aspecified treat rate to appropriate gasoline or aviation gasolinecompositions. This invention provides a unique and novel approach toanti-VSR additives, resulting in a soft, easy-to-clean, non-toxic thinresidue film which coats the combustion area of the cylinder, pistonhead, intake and exhaust port areas, thereby treating VSR(wear-and-tear) to the mechanical parts.

The Additive of the present invention is tailored to work with anygasoline, but also finds particular advantage in use with clean-burninggasoline to treat VSR. Without being bound to any particular mechanismof action, it appears that the VSR Additive produces a very thin layerof a soft, easy to clean, non-toxic residue which accumulates and thenstabilizes in the combustion chamber. This produces a minimal but usefulbuildup of soft, white residue in and around the intake and exhaustports during the combustion process. The result is a thin, soft residuethat serves as a barrier to treat valve seat recession and to leave thecombustion chamber with virtually no wear-and-tear on the valve seat andwith freedom from harmful deposits.

The Additive is useful limiting VSR. As used herein, the reference to“limiting” VSR is meant to include a reduction of VSR as compared tooperation of the engine with the same fuel formulation, but without theAdditive. This reduction may include, for example, a reduction in VSR ofat least 10%, preferably at least 25%, and most preferably at least 50%.In some embodiments, the Additive is effective to substantiallyeliminate VSR, meaning that VSR is reduced by at least 90%. Inembodiments, use of the Additive eliminates VSR.

A major difference between the Additive of this invention and thosecommonly known in the prior art is its low treatment rate the Additiveresults in harmless deposits and less residue with a cleaner combustionchamber, which extends maintenance cycles and engine life while allowingfor ease of cleaning of spark plugs. It is a particular feature of thisinvention that the Additive package is free of an octane booster and/ora chemical scavenger, and in an aspect the final fuel formulationincluding the Additive is free, and preferably substantially free, of anoctane booster and/or a chemical scavenger. Being substantially freerefers to the final fuel formulation constituting less than 1 wt % ofoctane booster and/or chemical scavenger.

Calcium Sulfonates

The inventive Additive includes one or more fuel-soluble calciumsulfonates. The calcium sulfonates preferably comprise calcium petroleumsulfonates. In one embodiment, the calcium is provide to provide a lowtreat rate ranging from about 5 to about 100 ppm (as Ca²⁺),alternatively at least 5 or 10 ppm, in the fuel formulation.

Sulfonates can be derived from petroleum fractions, from lignin, andfrom fatty oils.

These materials are mixtures of indeterminate or variable composition,probably comprising one or more of the main chemical types of sulfonatestogether with sulfates and other sulfur compounds. Such compositions aremade largely by empirical procedures. Natural petroleum sulfonates aredefined as those manufactured by sulfonation of crude oil, crudedistillates, or any portion of these distillates in which hydrocarbonspresent are not substantially different from their state in the originalcrude oil. For further information, seehttps://www.primaryinfo.com/technology/calcium-petroleum-sulfonate.htm,the content of which is hereby incorporated by reference.

These natural materials, then, are quite different from syntheticsulfonates, which are derived most commonly from sulfonation of olefinicpolymers or alkyl aromatic hydrocarbons. Calcium petroleum sulfonate iscalcium salt of sulfonic acid made by processing heavy alkaline benzeneof suitable fraction with sulfuric acid or sulfur trioxide and refiningby liquid extraction by using suitable alcoholic solvent andprecipitating insoluble salts by control of PH and centrifuging.Petroleum sulfonate is mainly obtained by treating high-boilingpetroleum fractions in a stirred tank reactor (STR) or in a falling-filmreactor (FFR). Synthesis of petroleum sulfonate surfactant may be madewith ultra-low interfacial tension in a rotating packed bed reactor.

Sulfonation may be defined as any chemical process by which the sulfonicacid group (SO₂OH) or the corresponding salt or sulfonyl halide group(e.g. —SO₂Cl) is introduced into an organic compound. Recently a processhas been developed for the manufacture of superior metal petroleumsulfonates, particularly calcium petroleum sulfonates, by thesulfonation of a highly viscous, highly refined paraffinic oil fractionhaving a viscosity of at least about 200 to 230 SUS at 210 F, and havinga viscosity index of about 85 to 100 or higher.

Carriers

The calcium compound is preferably formulated in a compatible,low-toxicity carrier suitable for use in combination with gasolinefuels. As known in the art, such carriers include, for example, C₇ to C₉arene hydrocarbons.

Detergents

The Additive further may comprise one or more detergents. The detergentstypically comprise, for example, from 50 to 200 ppm of the Additive. Byway of example, a polyolefin alkyl phenol alkyl amine is a suitabledetergent. The use of such detergents in combination with the calciumsulfonates provides an unexpectedly superior impact on gasoline fuels byforming a thin soft residue layer without undesired build-up, whilestill being sufficient to treat valve seat recession when an engine isoperated continuously under load.

Detergents leave the intake clean, while the calcium forms a soft whitefilm during combustion which is easily cleaned by a light brush orrinsed with water and air dried. This is dramatically easier to cleanthan removing TEL or MMT organometallic deposits which form once fuel iscombusted and caked onto engine parts—requiring frequent and excessivephysical effort to clean off the spark plugs.

The use of a detergent will depend on the nature of the fuel. Forclean-burning fuels there will be less need for a detergent, whereasfuels which are not clean-burning may benefit from addition of adetergent. This is demonstrated in the examples provided hereafter. Thedetermination of the use of a detergent, and the amount, is within theordinary skill in the art based on assessment of the results of usingthe calcium sulfonate with a given fuel.

In a particular aspect, the detergent is used with the calciumsulfonates for addition to a fuel formulation requiring the detergent tomake the calcium sulfonates effective to limit VSR. As disclosed herein,certain fuels benefit from the combination of calcium sulfonates anddetergents in order to enhance the effect of either alone in limitingVSR. In this respect, the calcium sulfonates and the detergents are usedin amounts and proportions that increase the VSR limiting effect of thecalcium sulfonates. Preferably, the combination of the one or morecalcium sulfonates and the one or more detergents provides enhancedlimiting of VSR that is at least 25%, preferably at least 50%, betterthan use of the calcium sulfonates alone for a given fuel and engine.For example, if the calcium sulfonates limit VSR to 12%, then theaddition of the detergent results in a limitation of VSR to at most 9%,or at most 6%.

Antioxidant

An additional component may comprise an antioxidant, suitable for usewith fuel formulations. An example of a suitable antioxidant is2,6-ditertiary butyl-4-methylphenol. The determination of the use of anantioxidant, and the amount, is within the ordinary skill in the artbased on assessment of the results of using the calcium sulfonate with agiven fuel.

Other Excipients

Other known excipients may also be included in the Additive. Forexample, an anti-microbial agent, such as4,4,6-trimethyl-1,3,2-dioxaborolane, may optionally be included. It mayalso be desirable to add a color dye to the Additive formulation, forexample Blue (1,4-dialkylaminoanthraquinone), or Red(alkylazobenzene-4-azo-2-naphthol) dyes, or possibly other colors. Theaddition of such coloring agent may be prescribed by international fuelregulatory organizations (e.g. ASTM International) for quality controland color calibration when used in aviation gasolines.

Fuels

The use of >5% (m/m) aromatic hydrocarbons in aircraft piston engineshas an adverse effect on the output of exhaust emissions (particularlyin the absence of catalytic convertors as required in automobiles) andheavy combustion deposits of carbon. Using 30-50% aromatics (m/m) in thefuel, as is often the case in Autogas used in aircraft, increases thedensity of the fuel above 6 lbs. per gallon which may create a concernon managing center-of-gravity and weight/balance attributes of anaircraft. Accordingly, the preferred clean-burning gasoline is one with<5% aromatic hydrocarbons.

This invention is a specially designed Additive uniquely tailored towork with specific fuels, particularly clean-burning aviation gasolinesthat combust with very little or no organometallic, amines orhydrocarbon deposits—i.e. those fuels comprised of less than 5% (m/m)aromatic hydrocarbons, less than about 1.5% (m/m) aromatic amines andless than 0.005% (m/m) organometallic compounds that upon combustionleave very little or no residue on the valves. Such clean-burning fuelsmight expose the exhaust valves to direct (unlubricated) impact with thecylinder head, leading to valve seat recession.

Use of aromatic hydrocarbons >30% (m/m) increases the density of thefuel plus contributes to carbon fouling which has shown evidence ofimpacting sparkplug performance; also, excessive carbon fouling cancontribute to sticking/blow-by in the cylinder walls.

This Additive can be applied to any gasoline formulation for use in apiston engine, no matter the formulation, but is particularly usefulwhen used in very clean-burning unleaded gasoline blends comprised ofaliphatic hydrocarbons or any combination of aliphatic hydrocarbons andoxygenates as described herein.

The cleanest burning high-octane gasoline preferred an oxygenatecompound. Our scientists tested various known high-octane aviationgasolines (100LL, 100-octane with MMT, 100-octane with aniline) weretested. In addition we tested 100R, the cleanest burning oxygenatedaviation gasoline, which in various embodiments contained >80% EthylTert-Butyl Ether and ideally >95% ETBE, however some combination ofother ethers (MTBE, TAME, THME, Diisopropyl Ether, etc.) and traceamount of alcohols (methanol, ethanol, etc.) in the fuel as acceptablewithin industry limits on water solubility.

A further aspect of this invention is the Additive formulation in aclean-burning fuel eliminates the use of harmful chemicals that cancause acidity, corrosion, organometallic deposits and sparkplug fouling,and sludge build-up that by their chemical nature can cause unwantedwear-and-tear throughout the piston engine. Using this special Additivewith clean-burning gasoline results in less frequent and less extensiveengine maintenance requirements, conducted at longer time intervalsbetween servicing, thereby creating an economic benefit to operators ofaircraft piston engines.

Additive Package

In one aspect, the present invention provides an Additive package suitedfor addition to an existing fuel formulation. This addition could occurat any point in the preparation and use of a given fuel formulation. Forexample, during initial formulation of a fuel the calcium sulfonate maybe added to the other fuel components. The calcium sulfonate may beprovided by itself, or it may be in combination with other intended fuelcomponents. In a particular aspect, the calcium sulfonate forms acomponents of an Additive package that includes other componentsintended to work in combination with the calcium sulfonates, such asthose described herein including detergents and/or antioxidants. TheAdditive package may then also comprise a carrier effective to suspendor otherwise support, including by solution, the calcium sulfonates

In a related aspect, the Additive package is configured to be used foraddition to a fuel formulation as provided to an end user. For example,the Additive package may be separately contained and added directly tothe fuel in a storage receptacle or in the fuel tank of an aircraft orthe like. In this respect, the Additive package may be specificallysupplied with a combination of related components, e.g., the calciumsulfonates and other components such as carrier, detergent, antioxidant,dye, etc.

Method of Treating VSR

The present invention further includes a method of treating VSR usingthe Additive. The method comprises adding the Additive to a fuelformulation to provide the calcium sulfonates at a level to provide theconcentrations of calcium in the final fuel formulation as set forthherein. The method may comprise adding the Additive during the blendingof the fuel formulation. The method may also comprise adding theAdditive to the fuel formulation as it is received from the producer.This may occur by way of adding the Additive to the fuel while instorage or as present in a fuel tank, such as the tank of an aircraft.

Example 1—Prior Art

An aviation gasoline blend comprising at least one C₄-C₁₀ aliphatichydrocarbon and at least one oxygenated compound, with less than 5%arene hydrocarbons and no amines or organometallic compounds, having amotor octane of at least 99.6 MON was tested without any anti-VSRadditive. The result was an excessive level of valve recession as thefuel combustion ran “too clean” and the metal-on-metal impact of thevalves undesirably eroded the facing edge of the valves with the valveseat making the valve seat, out-of-tolerance after the 250 hours test ofengine operation.

Example 2—Phosphate

Aviation gasoline blend comprising at least one C₄-C₁₀ aliphatichydrocarbon and at least one oxygenated compound, with less than 5%arene hydrocarbons and no amines or organometallic compounds, having amotor octane of at least 99.6 MON was tested with a phosphorous-basedanti-VSR additive. The result was a limited level of valve recession,still within tolerance, but sludge and grime were excessive anddifficult to remove.

Example 3—Potassium

Aviation gasoline blend comprising at least one C₄-C₁₀ aliphatichydrocarbon and at least one oxygenated compound, with less than 5%arene hydrocarbons and no amines or organometallic compounds, having amotor octane of at least 99.6 MON was tested with a potassium -basedanti-VSR additive. The result was a limited level of valve recession,still within tolerance, but sludge and grime were excessive anddifficult to remove. Potassium tends to cake-up and form chunks ofdebris which can be dangerous when dislodged in the combustion orexhaust chamber.

Example 4—Manganese

Aviation gasoline blend comprising at least one C₄-C₁₀ aliphatichydrocarbon and at least one oxygenated compound, with less than 5%arene hydrocarbons and no amines or organometallic compounds, having amotor octane of at least 99.6 MON was tested with a manganese-basedanti-VSR additive (MMT). The result was a limited level of valverecession, but sludge and grime were excessive. Spark plug deposits shutdown the engine between regular cleaning intervals. MMT tends to cake-upand form chunks of debris which can be dangerous when dislodged in thecombustion chamber.

Example 5—Anti-VSR Additive

The response of the Additive package of this invention was tested inseveral different test engine runs using SAE standard testing for theresponse of the Additive package. The standard calls for a 250-hourtest, with the engine under full load. In total, 13 of these testengines were run the full 250 hours to evaluate additive response. Thistest was conducted on a nominal blend of 100R, a clean-burning aviationgasoline with 75% aliphatic hydrocarbons and 25% oxygenates (m/m) withthe maximum treat rate prescribed by the SPEC-100R-18 specification. Inaddition, 8 other full runs were conducted with decreasing amounts ofthe Additive package in this invention.

The piston engines were purchased new, fully dimensionally measured, andreassembled before the run. Oil was changed initially at 25 hours andthereafter every 50 hours. For comparison of data, 100LL avgas withtetraethyllead and ethanol-free automotive gasoline were each run on afull additive test engine. At the completion of each run, the testengine was torn down and completely measured, evaluated, andphotographed.

The following items were of specific focus as they relate to additiveresponse and an overall assessment of each attribute was compiled. Notethat VSR pass/fail was only one criteria of the test:

Intake Valve seat wear

Exhaust valve seat wear

Spark Plug—evaluation and photos

Cylinder head—evaluation and photos

Intake runner—evaluation and photos

Intake Valve stem—evaluation and photos

Exhaust Valve stem—evaluation and photos

Intake Valve face—evaluation and photos

Exhaust Valve face—evaluation and photos

Experiments were conducted comparing prior art fuel formulations ascompared to fuel formulations according to the present invention. Inaccordance with the guidance in D7826, the final test engine was run ona 100R with 4× treat rate of the recommended 10 ppm calcium Additivepackage (i.e. 40 ppm of calcium).

Results are summarized in the following tables. A FAIL criterion wasestablished for valve seat wear above 19% change from the pre-testmeasurements based upon industry service and manufacturer norms forvalve seat tolerance. The percent of VSR was determined by comparing thechange in measurement of a suitable structure of the engine, e.g., aridge on the edge of the valve seat. The tests were run based on a 200hour engine test.

TABLE 2 Intake Seat Exhaust Fuel ID Composition Additive Pack Treat RateWear Seat Wear PASS/FAIL 100LL AVGAS 100LL from KLAF UNKNOWN-directlyfrom pump 9.23% 1.30% PASS 91 AKI MOGAS 91 AKI Ethanol Free AutogasUNKNOWN-directly from pump 0.00% 15.87% PASS BASELINE 100R 2.75IsoB/72.25 IsoOCT/25 ETBE NONE 7.04% 63.51% FAIL

As evidenced in Table 2, 100LL avgas created lead deposits which allowedthe fuel to meet valve seat recession requirements. However, the leaddeposits required 25- to 50-hour inspections and cleaning. Autogastypically has up to 50% aromatics and high boiling compounds whichimpact the heavy exhaust valve deposits; autogas detergents may cleanthe intake. The 100R baseline fuel with no additives was spotless onboth valve seats, but regrettably the amount of valve seat wear was“high” due to the metal-on-metal impact (i.e., without appropriateadditives the fuel burns “too clean”, with no deposits).

TABLE 3 TA404 2.75 IsoB/72.25 IsoOct(K)/25 ETBE [VSR] 2.5 ppm Ca, [AO]10 mg/L 36.57% 85.94% FAIL TA401 2.75 IsoB/72.25 IsoOct/25 ETBE [VSR] 5ppm Ca, [DET] 50 ppm, [AO] 10 mg/L 18.31% 57.89% FAIL TA402 2.75IsoB/72.25 IsoOct(K)/25 ETBE [VSR] 7.5 ppm Ca, [AO] 10 mg/L 13.51%22.67% FAIL

Table 3 reports the results of using very clean-burning unleaded avgas100R (second column), and using small amounts of calcium (2.5 ppm, 5 ppmand 7.5 ppm) from calcium petroleum sulfonate, with 10 mg/L ofantioxidant (2,6-ditertiary butyl-4-methylphenol). The use of 7.5 ppm ofCa for test blend TA 402 yielded a passing result with respect to VSR.Addition of 50 ppm of detergent for test blend TA 401 helped clean theintake on TA401 and provided passing results.

TABLE 4 TA396 2.75 IsoB/72.25 IsoOct(P)/25 ETBE [VSR] 10 ppm Ca, [AO] 10mg/L 0.00% 0.00% PASS TA407 2.75 IsoB/72.25 IsoOct(K)/25 ETBE [VSR] 10ppm Ca, [DET] 50 ppm, [AO] 10 mg/L 0.00% 0.00% PASS TA409 2.75IsoB/72.25 IsoOct(K)/25 ETBE [VSR] 40 ppm Ca, [DET] 200 ppm, [AO] 10mg/L 0.00% 0.00% PASS

Using very clean-burning unleaded avgas 100R for the results in Table 4,and additive treat rates of at least 10 ppm of calcium, plus addingdetergents from 0 ppm up to 250 ppm and the antioxidant, made the entirevalve seat recession disappear and the combustion chamber was very cleanfrom any deposits.

Using very clean-burning unleaded aviation gasoline, blended in aminimum 99.6 MON formulation comprising at least one C₄-C₁₀ aliphaticand at least one oxygenated-compound, with no more than 5% aromaticcontent and with no amines or organometallic compounds, provided passingresults using an Additive containing at least 10 ppm calcium petroleumsulfonates plus anti-oxidants to result in no valve seat recession.

Furthermore, the optional addition of 50 ppm to 250 ppm of detergentsand the option of an anti-microbial agent results in cleanerpiston-engine intakes and long-time storability of the fuel, therebyextending overall engine life.

In one experiment, an aviation gasoline blend comprising at least oneC₄-C₁₀ aliphatic hydrocarbon and at least oxygenated compound, with lessthan 5% arene hydrocarbons and no amines or organometallic compounds,having a motor octane of at least 99.6 MON was tested with thecalcium-based anti-VSR Additive. The result was a level of valverecession of zero wear—like new. The calcium component of the additiveformed a thin white layer of soft film which prevented the valve seatfrom wearing during the 250-hour engine test. Additional testing foundthat the addition of detergents kept the intake clear from any depositsand dirt buildup. The antioxidant reduced the impact of any gum-formingcompounds. The anti-microbial agent reduced the risk of microbial growthin unleaded fuels that might be exposed to growth propagatingconditions.

Example 6

Exemplary formulations for the Additive are provided in Table 5.

TABLE 5 Tested VSR Additive Formulations (m/m) Anti- Detergent/ Anti-Carrier + VSR Antioxidant CI microbial Dye Additive 1 30-60% 40-70%Additive 2 10-40% 5-10% 20-50% 0% 20-40% Additive 3 20-30% 5-10% 20-30%20-30% 20-40% Additive 4 10-30% 5-10% 20-60%  5-20% 20-40%

The terms in Table 5 have the following meanings:

Anti-VSR=Calcium petroleum sulfonates

Anti-Oxidant=2,6-ditertiary butyl-4-methylphenol

Detergent/CI=Polyolefin alkyl phenol alkyl amine

Anti-microbial=4,4,6-trimethyl-1,3,2-dioxaborinane (Optional)

Blue Dye=1,4-dialkylaminoanthraquinone (Optional)

Red Dye=alkylazobenzene-4-azo-2-naphthol (Optional)

Carrier in Solution=C₇ to C₉ arene hydrocarbon

Aspects of the Invention

As described herein, the present invention has many aspects. Thesefurther include the following.

In a first aspect, the fuel Additive may be comprised of at least 10 ppmof calcium petroleum sulfonates in solution with a liquid carrier (an C₇to C₉ arene hydrocarbon), blended with any gasoline composition, whichupon combustion prevents valve seat recession, intake coking, andreduces post-combustion deposits in the exhaust chamber.

In a second aspect, the fuel Additive in the first aspect may be blendedspecifically with any aviation gasoline composition used in pistonaircraft, which upon combustion prevents valve seat recession, intakecoking, and reduces post-combustion deposits in the exhaust chamber.

The fuel Additive of the first or second aspect may be combined with 50to 250 ppm of detergent—such as Polyolefin alkyl phenol alkyl amine.

The fuel Additive of the first or second aspect may be combined with upto 20 mg/L of antioxidant-2,6-ditertiary butyl-4-methylphenol.

The fuel Additive of the first or second aspect may be combined with upto 40 mg/L of an anti-microbialagent-4,4,6-trimethyl-1,3,2-dioxaborinane.

The fuel Additive of the first or second aspect may be combined with anyapproved dyes for quality control and color calibration for fuel safety.

In a third aspect, a fuel Additive may be comprised of at least 10 ppmof calcium petroleum sulfonates in solution with a liquid carrier (an C₇to C₉ arene hydrocarbon), blended with any clean-burning aviationgasoline with at least a 99.6 MON octane rating, comprised of at leastone C₄ to C₈ aliphatic hydrocarbon and at least one oxygenated-compoundand with no more than 5% aromatic hydrocarbons, and no amines ororganometallic compounds, which upon combustion prevents valve seatrecession, intake coking, and reduces post-combustion deposits in theexhaust chamber.

The fuel Additive of the third aspect may be combined with 50 to 250 ppmof detergent—such as Polyolefin alkyl phenol alkyl amine.

The fuel Additive of the third aspect may be combined with up to 20 mg/Lof antioxidant—such as 2,6-ditertiary butyl-4-methylphenol.

The fuel Additive of the third aspect may be combined with up to 40 mg/Lof an anti-microbial agent—such as 4,4,6-trimethyl-1,3,2-dioxaborinane.

The fuel Additive of the third aspect may be combined with any approveddyes for quality control and color calibration for fuel safety—such asBlue Dye: 1,4-dialkylaminoanthraquinone and Red Dye:alkylazobenzene-4-azo-2-naphthol.

Further, the fuel Additive of any of the first, second or third aspectsmay comprise at least 10 ppm of calcium petroleum sulfonates in a liquidcarrier (an C₇ to C₉ arene hydrocarbon), blended with any combination ofspecified detergents, anti-oxidants, anti-microbial agents and dyes andsubsequently blended with any gasoline composition or aviation gasolinecomposition, which upon combustion prevents valve seat recession, intakecoking, and reduces post-combustion deposits in the exhaust chamber.

In a fourth aspect, a method of treating VSR in a fuel formulation maycomprise addition of a fuel Additive of the first, second or thirdaspects to yield a fuel formulation having the indicated amounts ofcalcium sulfonates in the final fuel.

In a fifth aspect, there is provided a fuel formulation comprisingcalcium sulfonates and other components, as disclosed herein, at amountsoperative to limit, or eliminate, VSR for the engine in which the fuelformulation is used.

While the invention has been illustrated and described in detail in theforegoing description, the same is to be considered as illustrative andnot restrictive in character, it being understood that only thepreferred embodiment has been shown and described and that all changes,equivalents, and modifications that come within the spirit of theinventions defined by following claims are desired to be protected. Allpublications, patents, and patent applications cited in thisspecification are herein incorporated by reference as if each individualpublication, patent, or patent application were specifically andindividually indicated to be incorporated by reference and set forth inits entirety herein.

1-5. (canceled)
 6. An aviation gasoline fuel formulation for use in anaviation engine, comprising: aviation gasoline comprising ETBE; one ormore calcium petroleum sulfonates in an amount of at least 5 ppmeffective to limit valve seat recession in the aviation engine using thefuel; and a detergent present in an amount to provide enhanced limitingof the VSR over that achieved with the calcium petroleum sulfonates toeliminate valve seat recession in the aviation engine using the fuel,the aviation gasoline comprising a clean-burning aviation gasoline withat least a 99.6 MON octane rating comprised of at least one C₄ to C₈aliphatic hydrocarbon and at least one oxygenated-compound and with nomore than 5% m/m aromatic hydrocarbons, and no more than 1.5% m/m aminesand/or no more than 0.005% m/m organometallic compounds, whichformulation upon combustion prevents valve seat recession and intakecoking, and reduces post-combustion deposits. 7-9. (canceled)
 10. Thefuel formulation of claim 6 in which the detergent is polyolefin alkylphenol alkyl amine to prevents intake coking and reduces post combustiondeposits.
 11. The fuel formulation of claim 10 which further includesthe antioxidant 2,6-ditertiary butyl-4-methylphenol in an amount up to20 mg/L.
 12. The fuel formulation of claim 11 which further includes theanti-microbial agent 4,4,6-trimethyl-1,3,2-dioxaborinane in an amount upto 40 mg/L.
 13. The fuel formulation of claim 12 which further includesa dye for quality control and color calibration for fuel safety. 14-20(canceled)
 21. The fuel formulation of claim 6 comprising no aromatichydrocarbons, no amines and no organometallic compounds.
 22. The fuelformulation of claim 6 comprising 5-10 ppm calcium petroleum sulfonates.23. The fuel formulation of claim 6 comprising at least 10 ppm calciumpetroleum sulfonates.